This application claims benefit of priority under 35USC xc2xa7 119 to Japanese Patent Application No. 2000-95082, filed on Mar. 30, 2000, the contents of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates generally to a magnetic head and a method for producing the same, and magnetic recording and/or reproducing system.
2. Description of Related Art
It is generally known that the efficiency of a magnetic head is rapidly improved as the magnetic path length of a magnetic circuit decreases. For example, as shown in FIG. 18A, the efficiency is rapidly improved as the magnetic path length decreases to 2 xcexcm (=2000 nm) or less. As shown in FIG. 18B, the magnetic path length means the length of a magnetic circuit passing through a magnetic substance portion 52a, magnetic substance portion 53a, magnetoresistance effect element (e.g., GMR (giant magnetoresistance effect) element), magnetic substance portion 53b and magnetic substance portion 52b of a magnetic head.
The construction of a first example of a conventional magnetic head is shown in FIG. 19. This conventional magnetic head comprises a pair of magnetic substance portions 51a and 51b which are constructed so as to form two different gaps G1 and G2, and a magnetoresistance effect element 56 which is provided in the gap G2. The construction of a second example of a conventional magnetic head is shown in FIG. 20. The magnetic head in this second example comprises a pair of magnetic substance portions 52a and 52b which are arranged so as to be spaced from each other by a gap G1, a pair of magnetic substance portions 53a and 53b which are arranged so as to be spaced from each other by a gap G2 which is greater than the gap G1, and a magnetoresistance effect element 56 which is formed as a bridge between the magnetic substance portions 53a and 53b. In the first and second examples, the gap G1 is formed so as to be more close to a medium facing surface than the gap G2.
The magnetic substance portions 51a and 51b of the magnetic head in the first example are formed by lithography at separate steps, respectively, and the pair of the magnetic substance portions 52a and 52b and the pair of magnetic substance portions 53a and 53b of the magnetic head in the second example are formed by lithography at separate steps, respectively.
Therefore, there is a limit to the formation of a fine magnetic path due to an alignment error and the resolution of a photolithography system. For example, even if an advanced stepper is used, there is an alignment error due to the mechanical alignment precision (50 nm) of the stepper and the deformation of the substrate, so that an error of 400 nm is caused. In order to decrease the producing costs, an inexpensive excimer laser is often used for lithography. When the excimer laser is used, the resolution is about 200 nm. As can be seen from FIG. 21, the alignment error expresses a shift from the center of the gap G1, so that the whole alignment error is 800 nm (=400 nmxc3x972). For that reason, it is not possible to form a magnetic head having a magnetic path length which is equal to or less than a value (2000 nm) obtained by doubling a value (1000 nm) obtained by adding the resolution of 200 nm to the alignment error of 800 nm.
As shown in FIG. 21, in order to form a small magnetic path having a high efficiency, it is required to decrease both of the length G2 of a magnetic gap on the opposite side to a medium facing surface 58 and the height H from the medium facing surface 58 to a magnetoresistance effect element 58. In order to increase the line resolution, it is also required to decrease the length G1 of a magnetic gap on the side of the medium facing surface (about 50 nm).
However, in conventional magnetic head structures and conventional methods for producing the same, these requirements can not be satisfied.
Ironically, as can be seen from FIG. 18A, the efficiency of a magnetic head is rapidly improved when the magnetic path length is about 2000 nm or less which can not be formed in the prior art. Even if a small magnetic path is formed by a conventional magnetic head structure, the efficiency is rapidly lowered in the reproduction of a shorter wavelength signal (0.1 xcexcm or less) required in recent years although the reason for this is not clear, so that it can not be used as a high-density recording head. This is the same during a recording operation, not only during a reproducing operation. In conventional recording heads, the efficiency is greatly lowered in the recording at a shorter wavelength although the reason for this is not clear, so that it is not possible to record on low noise medium for a high density, which exceeds 50 Gbpsi (Giga bit per square inch), using current which can be supplied by a recording IC (Integrated Circuit).
It was found that the lowering of the recording/reproducing efficiency in a shorter wavelength region was remarkable when the length of a magnetic path approaches the order of the thickness (100 nm) of a magnetic domain wall of a magnetically soft substance.
As described above, in all of the conventional head structures, a thin-film is patterned by lithography to form a magnetic circuit. Therefore, even if a small magnetic circuit is intended to be formed, there is a limit to the increase of the efficiency of the head. Moreover, even if a desired head can be available with low yields, there is a problem in that the recording/reproducing efficiency at a shorter wavelength is greatly lowered so that it is not possible to record/reproduce at a high density.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a magnetic head capable of recording or reproducing with a high efficiency even in the case of a shorter magnetic path length and a shorter wavelength signal, a method for producing the same, and a magnetic recording and/or reproducing system using the same.
In order to decrease the magnetic path length as short as possible, a magnetic head shown in, e.g., FIG. 17, is considered. That is, a pair of magnetic substance portions 54a and 54b are arranged so as to spaced from each other by a predetermined gap G, and a magnetoresistance effect element 56 is provided so as to construct a bridge between the magnetic substance portions 54a and 54b. 
This magnetic head can not be used as a high-density magnetic head since it has a low reproducing efficiency or a bad reproducing resolution although it is suited to decrease the magnetic path length. That is, when the magnetic gap length G is small, most of magnetic fluxes from the medium flow into the magnetic gap, and only part of magnetic fluxes flow into the magnetoresistance effect element, so that it is not possible to obtain a great output. On the other hand, when the magnetic gap length is great, the line resolution is extremely bad, so that the magnetic head is not worth being used as a tip magnetic head for high density.
Therefore, in order to accomplish the aforementioned and other objects, the inventors have invented a magnetic head having the following construction and a method for producing the same.
According to a first aspect of the present invention, a magnetic head comprises: a pair of magnetic bodies comprising respective first and second medium facing surfaces, respective first and second rear surfaces opposite to the medium facing surfaces, and respective inner side surfaces, the inner side surfaces facing each other; and a magnetic gap disposed between the inner side surfaces and comprising third medium facing surface coplanar with the first and the second medium facing surfaces and third rear surface coplanar with the first and second rear surfaces; one of the inner side surfaces satisfying relationships of
x=G1/2 with respect to 0xe2x89xa6yxe2x89xa6TH, and
0.1xc2x7tan{2(xxe2x88x92G1/2)}+THxe2x89xa6yxe2x89xa65xc2x7tan(2(xxe2x88x92G1/2))+TH with respect to THxe2x89xa6y
where x represents X-coordinate of the one of the inner side surfaces and y represents Y-coordinate of the one of the inner side surfaces, the X-axis extends from a center of the third medium facing surface toward a center of the first or the second medium facing surface, the Y-axis extends from the center of the third medium facing surface toward the third rear surface, the Y-axis is substantially perpendicular to the X-axis, and G1 and TH respectively represent constants.
It is preferred that y continuously varies from a point, y=TH, to the first or second rear surface as x continuously increases from a point, x=G1/2.
The pair of magnetic bodies may comprise protruding portions of magnetically soft substance on the first or second medium facing surfaces on both sides of the magnetic gap.
The pair of magnetic bodies are magnetic yokes, and the magnetic head may further comprise a magnetoresistance effect element arranged on the first and second rear surfaces and disposed over the magnetic gap.
The pair of magnetic bodies are magnetic cores, and the magnetic head may further comprise: a rear yoke of magnetically soft substance provided on the first and second rear surfaces and disposed over the magnetic gap, and a recording coil formed in the magnetic gap.
According to a second aspect of the present invention, a magnetic recording head comprises: a pair of magnetic bodies spaced apart with a magnetic gap therebetween and comprising respective medium facing surfaces and respective rear surfaces opposite to the medium facing surfaces, one of the pair of magnetic bodies comprising a protruding portion, the protruding portion being tapered off toward the medium facing surface; a recording coil provided in the magnetic gap; and a rear magnetic body of magnetically soft substance disposed on the rear surfaces and disposed over the magnetic gap.
According to a third aspect of the present invention, a magnetic reproducing head comprises: a pair of magnetic bodies spaced apart with a magnetic gap therebetween and comprising respective medium facing surfaces and respective rear surfaces opposite to the medium facing surfaces, one of the pair of magnetic bodies comprising a protruding portion, the protruding portion being tapered off toward the medium facing surface; and a magnetoresistance effect element disposed on the rear surfaces and disposed over the magnetic gap.
According to a fourth aspect of the present invention, there is provided a method for producing a magnetic head, comprising: forming a magnetic body on a substrate, the magnetic body comprising a principal plane facing the substrate and a rear plane opposite to the principal plane; applying beam to the rear plane of the magnetic body and forming a portion defining a hole extending from the rear plane to the principal plane; forming a magnetic gap in the hole; and separating the magnetic body and the magnetic gap from the substrate and forming medium facing surface substantially coplanar with the principal plane.
The beam is preferably focused ion beam.
According to a fifth aspect of the present invention, there is a method for producing a magnetic head comprising: forming an insulating film on a substrate; applying focused ion beam to the insulating film in a direction toward the substrate, and forming a portion defining first and second trenches in the insulating film; filling magnetic substance in the first and second trench to form a pair of magnetic bodies; forming a recording coil in the insulating film between the pair of magnetic bodies; and forming a second magnetic body on the pair of magnetic bodies and the recording coil.
According to the magnetic head with the above described construction according to the first aspect of the present invention, the magnetic gap is formed so as to meet the above described relational expressions, so that: it is possible to enhance the reproducing efficiency even in the case of a shorter magnetic path length and a shorter wavelength signal. In addition, it is possible to decrease the length of the magnetic gap on the side of the recording medium, so that it is possible to enhance the resolution.
According to the magnetic recording head with the above described construction according to the second aspect of the present invention, it is possible to decrease the height of one of the magnetic bodies having the protruding portion, i.e., the distance between the surface of the protruding portion facing the recording medium and the rear surfaces, so that it is possible to decrease the magnetic path length and to greatly improve the recording efficiency. In addition, the protruding portion has the shape tapered off toward the medium facing surface, it is possible to further improve the efficiency when shorter wavelength signals are recorded.
According to the magnetic reproducing head with the above described construction according to the third aspect of the present invention, it is possible to decrease the height of one of the magnetic bodies having the protruding portion, i.e., the distance between the surface of the protruding portion facing the recording medium and the rear surfaces, so that it is possible to decrease the magnetic path length and to greatly improve the recording efficiency. In addition, the protruding portion has the shape tapered off toward the medium facing surface, it is possible to further improve the efficiency when shorter wavelength signals are recorded.
According to the magnetic head producing method with the above described construction according to the fourth aspect of the present invention, the beam is applied to the rear plane of the magnetic body and the hole is formed to extend from the rear plane to the principal plane and the magnetic gap is formed in the hole. Thus, it is possible to form a desired magnetic gap, the length of which is small on the side of the principal plane and continuously varies toward the rear plane, and it is possible to decrease the magnetic path length as small as possible, so that it is possible to obtain a magnetic head capable of efficiently carrying out a reproducing operation even in the case of a shorter wavelength signal.
According to the magnetic head producing method with the above described construction according to the fifth aspect of the present invention, the focused ion beam is used for forming the first and second trenches in the insulating film, and the first and second trenches are filled with the magnetic substance to form the pair of magnetic bodies. Thus, it is possible to obtain the pair of magnetic bodies having desired shapes, and it is possible to decrease the magnetic path length, so that it is possible to obtain a magnetic head having a greatly improved efficiency when shorter wavelength signals are recorded.